Date: Mon, 11 Feb 2008 06:32:06 -0500
From: Alan Cox <alan@redhat.com>
To: Tejun Heo <htejun@gmail.com>, linux-kernel@vger.kernel.org,
       linux-ide@vger.kernel.org, alan@redhat.com, jeff@garzik.org
Subject: Re: [PATCH] libata: Forcing PIO0 mode on reset must not freeze system
Message-ID: <20080211113206.GD28762@devserv.devel.redhat.com>
References: <20080210195556.GA5261@homac> <47AFB4DB.1000204@gmail.com> <20080211102907.GC4646@homac.suse.de>
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On Mon, Feb 11, 2008 at 11:29:07AM +0100, Holger Macht wrote:
> > In the above example, even the reset sequence itself can cause hang if
> > the hardware is implemented slightly differently.  The reason why
> > set_piomode() locks up but reset sequence doesn't is simple dumb luck.
> 
> Another thing, whether it's poor luck or not, it worked like this than at
> least 2.6.22. And it was _heavily_ tested. The above commit broke it
> between 2.6.24-rc1 and 2.6.24-rc2, which is at least a regression.

Not neccessarily. It may just be timing chance on your box.

I agree however we should be doing the reset after the PIO0 switch if it
turns out that the precise order of the two events matters.

Alan

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